Electric incandescent lamp

ABSTRACT

This invention relates to electric incandescent lamps having a tungsten filament and a bulb made of heat-resistant and pervious material such as quartz glass in which boron tribromide is provided constituting a reactive transport gas for establishing the regenerative cycle in addition to the usual inert gas such as argon and nitrogen. Thereby various faults inevitable in the usual incandescent lamps filled with a regenerative gas in the form of various halogen compounds are avoided or are overcome, and maintain a rather longer life. When boron tribromide is filled in the amount ranging from 0.8 X 10 7 to 2.0 X 10 5 gram molecule per 1 cm.3 of inner volume of the bulb, the bulb life can be considerably extended.

United States Patent [72] Inventors Tashio Takahashi Tokyo; Utami Mikarni, Gyoda; Shigeru Suzuki, Kumagaya; llideyuki Sato, Gyoda, all of, Japan [21] Appl. No. 846,475

[22] Filed July 31,1969

[45] Patented June 1, 1971 [73] Assignee lwasaki Denki Kabushiki Kaisha Tokyo, Japan [32] Priority Aug. 13, 1968, May 21, 1969 [31] 43/57260 and 44/38729 [54] ELECTRIC INCANDESCENT LAMP 5 Claims, 2 Drawing Figs.

[52] U.S.Cl 313/174, 313/222, 313/223 [51] Int. Cl H0lk 1/50 [50] Field (Search 313/174,

[56] References Cited UNITED STATES PATENTS 1,944,825 1/1934 Millner 313/174 Primary Examiner-Raymond F. Hossfeld Attorney-Waters, Roditi & Schwartz ABSTRACT: This invention relates to electric incandescent lamps having a tungsten filament and a bulb made of heat-resistant and pervious material such as quartz glass in which boron tribromide is provided constituting a reactive transport gas for establishing the regenerative cycle in addition to the usual inert gas such as argon and nitrogen. Thereby various faults inevitable in the usual incandescent lamps filled with a regenerative gas in the form of various halogen compounds are avoided or are overcome, and maintain a rather longer life. When boron tribromide is filled in the amount ranging from 0.8Xl0 to 2.0 l0 gram molecule per 1 cm. of inner volume of the bulb, the bulb life can be considerably extended.

ELECTRIC INCANDESCENT LAMP This invention generally relates to an electric incandescent lamp comprising a tungsten filament provided in a bulb which is made of heat-resistant or high melting point and pervious material such as quartz glass and filled with a halogen constituting an active transport gas in addition to the usual inert gas, and more particularly to such lamp containing bromine in the form of a bromide compound.

It has been known to prevent the bulb wall of the incandescent lamp from being blackened due to deposit of tungsten throughout its useful life by filling the lamp with a reactive transport gas in addition to the inert gas such as argon and nitrogen so that said reactive gas may be chemically combined with evaporated tungsten and then the resulting tungsten compound decomposes to return metallic tungsten onto the filament according to the so-called regenerative cycle. It has been also in public knowledge to use a halogen such as iodine, bromine and chlorine as said reactive transport gas.

All of the known incandescent lamps containing such reactive transport gas, however, have been unsatisfactory in that there are various problems which are difficult to be technically solved. One problem is that tungsten filament portions of relatively lower temperature and metal portions other than the tungsten filament such as filament supports and lead conductors are apt to be corroded by said reactive gas. It is necessary in order to solve said problem to select the geometrical shape and dimensior. of the bulb and raise the tungsten filament to a considerably higher temperature so that said lower temperature metal portions in the bulb can not be corroded by the reactive transport gas. For that purpose, the incandescent lamp must be so designed, in case of the reactive transport gas being iodine, that the tungsten filament temperature may be kept at least at a temperature of 800 C. and the bulb wall at 250 C. at the lowest. It will be appreciated that in case of said gas being bromine or chlorine the bulb is to be. sodesigned as to keep said temperatures higher than the above.

Another problem is that when a halogen gas is charged into the bulb as in the form of the element, some portions of the lamp-manufacturing machine such as devices for evacuating air and filling the halogen gas are easily corroded. Above all when iodine is to be used, it is difficult to charge the bulb therewith in the correct amount necessary for establishing the regenerative cycle due to its vapor pressure which is lower at room temperature than'the charging pressure necessary for the regenerative cycle. In order to solve the problem as referred to above, it has been proposed to use the reactive transport gas in the form of halogen compounds such as hydrogen halide, and hydrocarbon halide. In the specification of U.S. Pat. No. 3,091,718 issued on May 28, 1963 .to J. Shurgen it is disclosed that the Constant Lumen Maintenance Lamp may be manufactured without the difficulties as referred to above when the gas is-filled in thebulb-in theform of hydrogen halide, such as hydrogen iodide, bromide or chloride. It is proposed in the specification of U.S. Pat. No. 3,418,512 issued on Dec. 24, l969to G. R. TJampens et al. to use a halogen as reactive transport gas not only in 'the formof hydrogen halideas referred to in said U.S. Pat. No. 3,091,718 but also in the form of hydrocarbon halide such as hydrocarbon bromide and chloride.

As hydrogen halides and hydrocarbon halides-as recommended in said U.S.-patents areof. lower boiling ,point andstable at room temperature, said difficultiesto be encountered when the incandescent lamps are being manufactured may be surely solved. It has been appreciated as aresultof various experiments, however, that if hydrogen halide .or hydrocarbon halide is used, hydrogen to be releasedon the operation of the lamp acts to hinder the regenerative cycle whensaid halogen is iodine, and causes an early blackening on the bulb inner surface. When the halogen is bromine or chlorine, hydrogen may effectively serve as a buffer gas but it has been reportedly necessary in this case to provide some means forpreventing hydrogen from diffusing through the bulb wall during the operation.

An essential feature of this invention is, thus, to provide an incandescent lamp as comprising a tungsten filament provided in a quartz glass bulb which is filled with bromine in the form of boron tribromide constituting a reactive transport gas in addition to the usual inert gas, thereby having no difficulties to be encountered on or during the manufacture ofincandescent lamps of the type as referred to nor structural faults which are inevitable in said type lamps, with maintaining a rather longer life than such conventional incandescent lamps.

, and beneficial effects.

Preferred embodiments of the invention shall be explained hereinafter in more detail with reference to the accompanying drawing in which;

FIG. 1 is a plan view of an incandescent lamp for projectors or cinematographs, and

FIG. 2 is a similar view of an incandescent lamp for general illuminations.

In FIG. 1, a reference numeral 11 represents a cylindrical bulb made of a quartz glass, 12 a single coil tungsten filament contained in said bulb ll, 13 and 14 legs for supporting said filament l2, l5 and 16 molybdenum foils welding fixed respectivelyto each of said support legs 13 and 14 at the outer ends thereof, 17 and 18 lead conductors connected respectively to each of said molybdenum foils 15 and 16, 19 presssealed portion of the bulb 11. The bulb 11 was made in such a dimension as the outer diameter is 13 mm., and the inner diameter and length are respectively 10 mm. and 15 mm. so as to form 1.5 cm. inner volume of the bulb. The electrical load to the tungsten filament was 24v.l50w. Characteristics of the incandescent lamp as referred to above in which boron tribromide was charged in addition to argon were as in table 1 depending on the amount of the filled boron tribromide ranging from 0.6X10" to 2.5 l0 gram molecule per 1 cm. of the bulb inner volume.

TABLE 1 All Luminous Color Filled 3B Br (gram Average luminous efiiciency temp. molecule/cm!) life (hr.) flux (1111.) (1m./w,) (K.)

0.6 l0- 60 1 4, 700 1 31. 3 3, 400 Z 4, 700 2 31.3 3, 400 90 2 4, 700 2 31.3 3, 400 90 2 4, 700 Z 31. 3 3, 400 Z 4, 700 1 31.3 3, 400 90 2 4, 700 2 31. 3 3, 400 90 2 4, 700 2 31.3 3, 400 90 Z 4, 700 2 31. 3 3, 400 90 2 4, 700 I 31. 3 3, 400 2.5Xl0- 60 2 4, 700 2 31. 3 3, 400

1 Initial. 2 Over.

As to the incandescent lamp as illustrated in FIG. 1, the electric load to the tungsten filament 12 was made 24v.-25 0w., the dimension of the bulb l was so selected as '13 mm. outer diameter, 10 mm. inner diameter and 25 mm. length to form 2.5 cm. inner volume. Into said bulb 1 charged was boron tribromide in the amount ranging from 2.0X10" to 5.0 Xl0' gram moleculeper '1 cm inner volume of the bulb in addition to argon gas. The characteristics of the incandescent lamp were varied as shown in table 2 depending on the respective value of the amount of boron tribromide as filled.

As appreciated from the above tables, it is possible to produce such incandescent lamps as having average life of about 80 to I hours when boron tribromide is charged into the bulb in the amount ranging from 0.8Xl0 to 2.O l0 gram molecule in addition to argon gas. Since it has been reported that the average life of the conventional incandescent lamps of the similar type is about 50 to 60 hours, this invention can obviously provide considerably long life incandescent lamps. Said tables show also that even if the amount of boron tribromide is varied within the range of 0.8Xl0 to 20x10" gram molecule the average lamp life is hardly varied. This means that should some error arise as to the amount of boron tribromide filled in the bulb when manufacturing the incandescent lamps, the characteristics of the products would not fluctuate substantially, and consequently it can be said that it is relatively easy to control the amount of boron tribromide provided in the lamps.

The invention was applied also to such an incandescent lamp for general illumination as illustrated in FIG. 2 and similarly desirable results were obtained.

In FIG. 2, a reference numeral 21 represents a cylindrical bulb made of quartz glass, 22 coiled tungsten filament, 23 and 24 inner lead conductors connected respectively to each of the opposite ends of the tungsten filament 22, 25 and 26 molybdenum foils weldingly fixed respectively to each of the outer ends of the lead conductors 23 and 24, 27 and 28 outer lead conductors weldingly connected respectively to each of the outer ends of the respective molybdenum foils 25 and 26, and 29 and 30 press-sealed portions of the bulb 21.

In the incandescent lamp of such structure, the electric load to the tungsten filament 22 was made l00v.-500w., and the dimension of the bulb 21 was so selected such that its outer diameter was 13 mm., its inner diameter mm. and its length 44 mm. so as to form 3.2 cm. inner volume of the bulb, in which boron tribromide was charged in the amount ranging from l.0Xl0 to l.5Xl0 gram molecule per 1 cm. inner volume of the bulb in addition to the mixture of argon and nitrogen as inert gas. The characteristics of the incandescent lamp were as in table 3 depending on the value of the charging amount.

As clearly seen from said table, the average life of the incandescent lamps according to this invention was about 3,000 hours, which is considerably longer than 2,000 hours reported as being of the average life on the conventional incandescent lamps of the similar type.

It has not yet been made clear what action and in what manner boron tribromide effects the incandescent lamp during the operation thereof, but there has been established the following regenerative cycle between tungsten and bromine;

BBr B+3/2 Br; (1) W-l-2 Br SWBn The reaction formula l means boron tribromide is decomposed at the higher temperature portion in the bulb adjacent the tungsten filament into bromine and boron to generate molecular bromine necessary for the regenerative cycle. The equation (2) means molecular bromine formed according to the formula (1) is chemically combined with tungsten evaporated from the filament to form tungsten bromide which may be again decomposed at the higher temperature portion in the bulb into tungsten and bromine. Boron as being in the bulb but not taking part in the regenerative cycle is considered to form boron tribromide again at the lower temperature portions in the bulb according to the reaction reverse to that as represented by the formula l so as to maintain equilibrium.

What we claim is:

1. An incandescent electric lamp comprising a bulb constituted of heat-resistant and light-transmitting material, a tungsten wire filament mounted in said bulb and having opposite ends, lead conductors sealed and extending through at least one end of said bulb and electrically connected respectively to each of the ends of said filament, said bulb being filled with an inert gas and with a halogen, said halogen constituting a reactive transport gas, said halogen being constituted of boron tribromide, the quantity of said boron tribromide ranging from 0.8Xl0 to 2.0 l0 grarn molecule per 1 cm. of inner volume of the bulb.

2. An incandescent electric lamp as claimed in claim 1 wherein said bulb includes opposite end portions, said lead conductors extending through said end portions respectively.

3. An incandescent electric lamp as claimed in claim 1 including a pair of metallic foils interconnecting said lead conductors to said ends of said filament respectively.

4. An incandescent electric lamp as claimed in claim 3 wherein said metallic foils are each constituted of molybdenum.

5. An incandescerit electric lamp as claimed in claim 1 wherein said filament is constituted .of a helical coil.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 582, 703 Dated June 1, 1971 Inventor) Toshio Takahashi et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Abstract, line 11, "10 should read 10 same line ll, "10 should read l0 Column 2, lines 16,

41, 63 and 64, Column 3, lines 4 and 10, and Column 4, line 37,

"10 each occurrence, should read l0 Column 2, lines 16 and 41, and Column 3, lines 4, 10 and 37, and column 4, line 37, "10 each occurrence, should read 10' Column 3,

line 37, "10 should read 10' Signed and sealed this 20th day of June 1972.

(SEAL) Attest:

EDWARD MFLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents I FORM PO-1050 (10-69) USCOMM-DC 60376-5 59 Q USv GOVERNMENT PRINTING DFFICE ISIS O-SiG-Jll 

1. An incandescent electric lamp comprising a bulb constituted of heat-resistant and light-transmitting material, a tungsten wire filament mounted in said bulb and having opposite ends, lead conductors sealed and extending through at least one end of said bulb and electrically connected respectively to each of the ends of said filament, said bulb being filled with an inert gas and with a halogen, said halogen constituting a reactive transport gas, said halogen being constituted of boron tribromide, the quantity of said boron tribromide ranging from 0.8 X 10 7 to 2.0 X 10 5 gram molecule per 1 cm.3 of inner volume of the bulb.
 2. An incandescent electric lamp as claimed in claim 1 wherein said bulb includes opposite end portions, said lead conductors extending through said end portions respectively.
 3. An incandescent electric lamp as claimed in claim 1 including a pair of metallic foils interconnecting said lead conductors to said ends of said filament respectively.
 4. An incandescent electric lamp as claimed in claim 3 wherein said metallic foils are each constituted of molybdenum.
 5. An incandescent electric lamp as claimed in claim 1 wherein said filament is constituted of a helical coil. 